Recent research from the UK and California shows disturbing results: microplastics—other than just fibers from clothes—were found in human lungs in the UK study, and in human stool and placenta samples, according to the California research. Microplastics are defined as any plastic particles ranging in size from 5 mm and smaller—down to 1 µm (1 micron).
While the route of microplastics particles infection for the lungs is airborne, the routes of infection in other parts of the body are less well known, but the California study suggests these sources could be in food (especially fish and seafood) and drinking water. However, the effects of microplastics in the human body are largely not well understood (although inflammation is one possibility), but are generally accepted to be deleterious as are the chemical constituents found in most plastics.
The UK study, “Detection of Microplastics in Human Lung Tissue Using μFTIR (micro fourier-transform infrared) Spectroscopy,” was conducted by a research team from the University of Hull and the Hull York Medical School in collaboration with surgeons at Castle Hill Hospital in East Yorkshire, who supplied the live lung tissue. The California study, “Statewide Microplastics Strategy, Understanding and Addressing Impacts to Protect Coastal and Ocean Health,” was prepared by the State of California and several agencies working together to trace microplastics as they travel from industrial sources and careless handling of plastics by humans into various water bodies, including the Pacific Ocean.
In the Lungs
The UK research shows that inhaling microplastics is a route of exposure, but until this research was conducted, there have been few studies confirming the presence of microplastics in lung tissue. The UK study found that of the microplastics detected in lung tissue collected from live patients as part of their routine medical care, 12 types were discovered. Many of these plastics are commonly found in packaging, bottles, clothing, rope/twine and many manufacturing processes. For unknown reasons, higher levels of microplastics were found in male patients than in females.
These patients were not exposed to plastics in a factory setting—airborne or otherwise—where they may have been exposed to the chemicals used in making plastics. These chemicals have been shown to endanger human health. For example, in a 2011 paper entitled “Public Health Impact of Plastics: An Overview,” by Rustagi, Pradhan and Singh—and published on the NIH’s National Library of Medicine website—the authors stated that: “Exposure to harmful chemicals during manufacturing, leaching in the stored food items while using plastic packages or chewing of plastic teethers and toys by children are linked with severe adverse health outcomes such as cancers, birth defects, impaired immunity, endocrine disruption, developmental and reproductive effects etc.”
Using µFTIR spectroscopy with a size limitation of 3 µm, the UK study found 39 microplastics in 11 of the 13 lung tissue samples tested—considerably higher than any previous laboratory tests. Lung tissue was obtained from 11 patients—with two patients providing two samples from different lung positions—for a total of 13 samples from 11 patients.
“Microplastics have previously been found in human cadaver autopsy samples,” says Laura Sadofsky, lead author on the research project. “This is the first robust study to show microplastics in lungs from live people.”
The UK study showed 11 microplastics were found in the upper part of the lung, seven in the mid part and 21 in the lower part of the lung, which was unexpected. “We did not expect to find the highest number of particles in the lower regions of the lungs, or particles of the sizes we found,” says Sadofsky. “This is surprising as the airways are smaller in the lower parts of the lungs and we would have expected particles of these sizes to be filtered out or trapped before getting this deep into the lungs”
Of the microplastics detected, 12 polymer types were identified with polypropylene, PP (23%), polyethylene terephthalate, PET (18%) and resin (15%) the most abundant. Polymer types within lung tissue were identified as fragments (43%), fiber (49%) and film (8%).
According to researchers, while the fate of particles entering the lung, and their resulting biological effects in terms of inflammation responses, are well known for ultrafine particulates in the nanoparticle or particulate matter (PM) less than ten micrometers (microns), the effects of microplastic particle sizes in the UK study remain largely understudied.
Microplastics in Water and Food
The California research states microplastics have been observed in Monterey Bay, San Francisco Bay, the Greater Farallones National Marine Sanctuary, Lake Tahoe and in Southern California waterways, including preproduction plastic pellets (nurdles) that spill from manufacturing facilities and reach California’s beaches.
According to the California study, microplastics are not only a marine pollution problem, but also have been found nearly everywhere scientists have looked, from pristine mountain streams to agricultural soil, and within human placenta, stool samples, and lung tissue. Microplastics can enter the food web, where plastic particles can transfer into tissue, and expose humans to plastic-associated and endocrine-disrupting chemicals from seafood consumption.
California has developed a Statewide Microplastic Strategy that provides a multiyear roadmap in managing microplastics pollution. Multiple state agencies and external partners will work together to reduce the introduction of microplastics in California’s coastal ocean and other aquatic systems.
The California strategy outlines a comprehensive, two-track approach to manage microplastics in the state. The first track outlines immediate, “no regrets” actions and multi-benefit solutions to reduce and manage microplastic pollution, while the second track outlines a comprehensive research strategy to enhance the scientific foundation for microplastic monitoring, source identification, risk assessment, and development of management solutions.
In the first track, the goal is to eliminate plastic waste at the source—defined as the product, material or industry from which microplastics originate. Solutions include reducing factory waste and encouraging innovation to use less plastic material and look for alternative sourcing materials. Another approach is pathway intervention—such as stormwater or wastewater that moves plastic into larger streams and the ocean. Outreach and education are important to prevent and reduce plastic production, use and waste—a good example, the single-use grocery bag.
The second track research includes an ongoing Microplastics Health Effects Workshop to study the human and ecological health effects of microplastics in water, characterize current knowledge and identify research policies. One 2021 presentation, “Microplastic Characteristics and Their Relevance to Risk Assessment,” looked at microplastics in food and water and asked more questions than provided answers—hence the reason for doing more research. For example, a big question needing an answer: Which microplastic characteristics are most relevant and/or meaningful for risk in food and water (e.g., size, shape, particle counts, polymer types)? Polymer type might matter depending on concentration. Particle size seems to be an issue when at lower concentrations when larger particles are more hazardous, but at higher concentrations, smaller particles are more problematic. Experiments are also needed to test whether polymer type and shape are drivers of toxicity.
Plastics and Soil
Beyond airborne and waterborne microplastics contamination, another potential source is soilborne microplastics, which can lead to waterborne contamination (seafood) and potential contamination with food through physical contact. While plastic litter and unsupervised trash dumps provide sources for plastics to infiltrate soil, another is the use of agricultural plastics. A recent United Nations working paper produced in 2021 for the UN Environmental Program (UNEP) and entitled, “Plastics in Agriculture: Sources and Impacts,” shows the problem with these materials as they are used in black and clear mulch, netting, bags, PVC piping, fertilizers, and the list goes on. Materials include HDPE #2, LDPE #4, PP#5, PP #6 and PVC #3. The UN paper suggests that as much as 23,500 metric tons of plastic and materials including microplastic particles are used annually in agriculture and horticulture in the European Economic area alone. Therefore, sources for microplastics entering the food and water supplies seem many.
Researchers have been busy creating new plastic formulations for films and solid containers that are designed to decompose naturally into safe molecules—thereby not damaging the environment or posing health concerns for ingesting materials. An FE Engineering R&D column in December 2019 explored an innovative decomposing film material. Most recently, the August 2022 Engineering R&D looked at a biodegradable material that could substitute for conventional polymer film or tray material for retail packaging of produce. The material is a replacement for conventional plastics and decomposes naturally into safe molecules.
Like single-use grocery store bags, plastic mulching material has the same environmental problem, says Mahesh Pradhan, coordinator of UNEP’s Global Partnership for Nutrient Management. It doesn’t go away quickly. Frequent soil sources of microplastic contamination include plastic tenting to protect plants from insects and birds and mulch films, which are used around plants to keep the soil moist and to keep weeds down. Another problem is the widespread use of plastic-encapsulated, slow-release fertilizers. Other plastic products include films for greenhouses and silage, shade and protection nets, and drip irrigation piping.
Some non-biodegradable plastic film products are being replaced by biodegradable materials. However, there is concern regarding the timeframe for degradation and the completeness of the process in the natural environment, says the UN paper. The rate of biodegradation of plastic in soil is influenced by soil moisture, UV-light, temperature, pH and the type and size of the plastic material. According to the UN paper, there is limited evidence that microplastics can move through the soil into plants and into food consumed by humans.
Mulch materials are typically made from low-density polyethylene (LDPE), which is largely produced from petroleum. Although LDPE is designed to be removed at the end of the harvesting season, some often remains and gets plowed into the soil for the next growing season. This is problematic, especially if a non-biodegradable mulch is used. The UN paper pointed out that in some areas where this type of mulch was used for 10 years, residual plastic levels measured in topsoil ranged from 50 to 260 kg/hectare or 44.5 to 232 lbs. per acre. This doesn’t count microplastic containing fertilizers or chemical contaminants used to make the LDPE.
“Detection of microplastics in human lung tissue using μFTIR spectroscopy;” Lauren C. Jenner, Jeanette M. Rotchell, Robert T. Bennett, Michael Cowen, Vasileios Tentzeris, Laura R. Sadofsky; Science of The Total Environment; Volume 831, 20 July 2022, 154907
“Statewide Microplastics Strategy: Understanding and Addressing Impacts to Protect Coastal and Ocean Health,” California Ocean Protection Council. (February 2022). Statewide Microplastics Strategy.
“Microplastics Health Effects Workshop,” Hosted by: SCCWRP, San Francisco Estuary Institute and University of Toronto—in coordination with the State of California Water Resources Control Board and the California Ocean Protection Council, https://www.sccwrp.org/about/research-areas/additional-research-areas/trash-pollution/microplastics-health-effects-webinar-series/
“20 Years of Government Responses to the Global Plastic Pollution Problem: The Plastics Policy Inventory;” Rachel Karasik, Tibor Vegh, Zoie Diana, Janet Bering, Juan Caldas, Amy Pickle, Daniel Rittschof, and John Virdin; Duke University, Nicholas Institute for Environmental Policy Solutions; 2020; 309 pp.
“Plastics in Agriculture: Sources and Impacts - Working Paper,” United Nations Environment Programme GRID-Arendal, December, 2021, UNEP
“Respiratory Protection,” United States Department of Labor, OSHA, Website
“Small Entity Compliance Guide for the Respiratory Protection Standard,” OSHA, 2011, 124 pp.